Chapter 2 Review

Scientific Method It is a 5 step process that outlines how to perform a proper experiment The steps are Observing and collecting Data Formulating a hypothesis Testing the Hypotheses Theorizing Publish results

Model vs. Theory Model Theory A model is an explanation of how a phenomena occur and how data or events are related A model can be any number of things visual, verbal or mathematical Theory A broad generalization that explains a body of facts or phenomena Theories can be composed of multiple models such as the atomic model is part of the atomics theory

Measurement Measurement represents a quantity or something that has magnitude, size, or amount The globally accepted scientific measurement is SI measurement

SI measurement Part 1 The SI measurement system is composed of seven base units

Si units Part 2 Si units can also have prefixes that make the unit either a larger or smaller number without having to write all of the zeros

Practice with Prefixes Kilometer Centimeter Decameter Millimeter 1,000 Meters 100 Meters 10 meters 1,000 meters

SI units Part 3 Units can be combined such as to find density you need to divide mass by volume These new units are called derived units

Practice with Derived Units If a box is, 1 meter tall, 2 meters wide, and 3 meters deep then what is its volume If the mass of an object is, 4 kilograms and a volume of 2 meters cubed then how dense is it 6 meters cubed 2 kilograms per meter cubed

Mass vs. Weight Weight is a measurement of the gravitational pull on an object usually by using springs Mass is a measurement done by using instruments like a balance

Accuracy and Precision Accuracy: the closeness of measurements to the correct value of the quantity Precision: the closeness of a set of measurements Which of the following are accurate? Which are precise?

Percentage Error The accuracy of a value can be compared with the correct value with the following equation:

Significant Figures Rules: •Zeros between nonzero digits are significant. •Zeros in front of nonzero digits are not significant. •Zeros at the end of a number and to the right of a decimal point are significant. •Zeros at the end of a number to the left of a decimal point is not significant, unless there is a decimal point after the number.

Significant Figures, cont. How many significant figures are in each of the following? 150. 3000 75.006 8522.0000 .098 3 1 8 2

Proportions Direct proportions Inverse Proportions if two quantities are directly proportional to each other then dividing one by another gives a constant value X/Y = K or Y=KX in which K is the constant This means that if X increases then Y must increase proportionally to keep K a constant Inverse Proportions Two quantities are inversely proportional to each other if their product is constant XY=K in which K is the constant This means that if X increases then Y must decrease proportionally to keep K a constant